EWD devices that adjust the amount of light to be transmitted by means of electrocapillarity (electro-wetting) are proposed. EWD devices display images with excellent brightness and contrast, and relatively low power consumption compared to many other display devices.
Referring to FIG. 6, this is a cross section view of part of a conventional EWD device before a voltage is applied thereto. The EWD device 10 includes a transparent substrate 11, a driving substrate 18 facing towards the transparent substrate 11, a first fluid 13, a second fluid 12, a plurality of side walls 16 and two support plates (not shown). The two support plates are provided between the two substrates 11, 18 for supporting the transparent substrate 11. Thereby, the two substrates 11, 18 and the two support plates define a sealed container (not labeled) for filling with the first fluid 13 and the second fluid 12. The side walls 16 are arranged in a lattice on an inner surface of the driving substrate 18 thereby defining a plurality of pixel regions P. The first fluid 13 is sealed within the sealed container corresponding to the pixel regions P. The second fluid 12 immiscible with the first fluid 13 is contacted to the first fluid 13 and filled in the sealed container.
The driving substrate 18 includes an insulating substrate 17, a plurality of electrodes 14 and a hydrophobic insulator 15. The electrodes 14 are provided on an inner surface of the insulating substrate 17 corresponding to the pixel regions P, and therefore forming a plurality of gaps 141 therebetween. The gaps 141 respectively correspond to the side walls 16. The hydrophobic insulator 15 covers the electrodes 14 and gaps 141.
When no voltage is applied, the first fluid 13 extends over an entire area in a direction that is orthogonal to the direction in which light is transmitted. Therefore, the light is shielded by the first fluid 13 and the EWD device 10 displays a black image.
Referring to FIG. 7, when a voltage 18 is applied to one of the electrodes 14 and the second fluid 12, an interface between the first fluid 13 and the second fluid 12 changes due to electrocapillarity, so that the second fluid 12 contacts the hydrophobic insulator 15. Thus, light emitted from the driving substrate 18 can pass through the second fluid 12, and the EWD device 10 displays a white image.
In general, for obtaining a colored displaying, a color filter can be provided between the transparent substrate 11 and the second fluid 12. Referring to FIG. 8, a conventional color filter 20 is shown. The color filter 20 includes a plurality of color filter units 21 arranged in a matrix corresponding to the pixel regions P. A black matrix 22 is provided between the color filter units 21 for separating the color filter units 21 having different colors.
However, when the color filter units 21 directly contact the second fluid 12 for a long time, the color filter 20 may be corroded by the second fluid 12. That is, durability of the EWD device 10 is decreased. To overcome this problem, a protective layer can be provided to prevent the color filter units 21 from contacting the second fluid 12. However, this may increase a thickness of the EWD device 10 and limit the compactness thereof.
What is needed, therefore, is an EWD device that can overcome the above-described deficiencies.